It is generally known in the art, for example, as disclosed in both US 2011/0020122 A1 and US 2008/0183403 A1, to monitor the health of structural members in systems.
In particular, it is known in the art to monitor the health of fan blades to assess if maintenance work needs to be carried out. This prevents unnecessary maintenance checks being undertaken and also provides earlier warnings of damage than routine checks.
Most known methods analyse each blade individually for damage. For example, U.S. Pat. No. 8,532,939 B2 discloses a system which measures the time of arrival of each blade of a fan at a certain position around the path of travel of the blade, and compares this with expected times of arrival of each blade. From the discrepancy between these, the system calculates the blade resonant frequencies and a comparison can be made to those of a “healthy blade”, to determine if there is blade damage.
A similar system is disclosed by US 2015/0285753 A1, which describes an array of magnetic fields for determining blade tip positional data. This data is used to calculate a measured blade vibrational frequency which is compared to an expected vibrational frequency to determine if a particular blade has incurred damage.
Similarly, US 2012/0045330 A1 teaches illuminating a wind turbine with a light source, building a 3-dimensional image of the wind turbine using backscattered light pulses and comparing this image with another to determine from the deviations if the health of the wind turbine has been compromised.
The present disclosure aims to provide an alternative and simple real-time health monitoring system for one or more propellers.